There have widely been used, as a hot melt adhesive which is used in disposable products such as a diaper and a napkin and is also applied to a base material thereof, for example, a nonwoven fabric, a tissue, a polyethylene film and the like, a synthetic rubber-based hot melt adhesive containing a thermoplastic block copolymer as a main component
In case of producing the disposable products, a film or a nonwoven fabric is coated with a hot melt adhesive, and high-speed coating is sometimes employed so as to enhance production efficiency of the disposable products. However, the synthetic rubber-based hot melt adhesive may be sometimes scattered when applied at a high speed.
One of means for enhancing the production efficiency of the disposable products includes a method in which an olefin-based hot melt adhesive typified by an ethylene-propylene copolymer is applied at a high speed.
JP 2001-96490 A and JP 2011-511866 A disclose that an olefin-based hot melt adhesive can be used in the disposable products. However, as is disclosed in JP 2001-96490 A and JP 2011-511866 A, the olefin-based hot melt adhesive is more suitable for use in paper processing than use in the disposable products.
JP 2001-96490 A discloses that a propylene polymer is used as a raw material for the hot melt adhesive. However, the hot melt adhesive in the same literature does not have sufficient wet adhesion to a tissue base material. A diaper, a sanitary napkin and the like often have a structure in which an absorber constituted by a pulp, an absorbent polymer and the like is wrapped in a tissue and the outside thereof is covered with a nonwoven fabric, a polyethylene film and the like. If the hot melt adhesive does not have sufficient wet adhesion, body fluid absorbency of the absorbent article may sometimes deteriorate by separation of adhesion between the tissues and by separation of adhesion between the tissue and the nonwoven fabric in a wet state.
As disclosed in the table of Examples, the hot melt adhesive of JP 2011-511866 A presupposes high viscosity and coating at about 170° C. to 180° C. Therefore, it is very difficult to coat a nonwoven fabric or a film with the hot melt adhesive of Patent Literature 2 in case of spiral coating at 160° C. or lower since the viscosity is too high.
Furthermore, not only the above-mentioned properties, but also little odor is required to the hot melt adhesive for disposable products.